1. Field of the Invention
The present invention pertains to a telemetry system for communicating data related to parameters such as pressure, flow, temperature and other parameters in a wellbore through a drill stem or tubing string by generating stress waves or controlled vibrations in the tubing string in the wellbore and sensing the vibrations with strain gauges and/or accelerometers disposed on the tubing string at or near the surface.
2. Background
A problem of longstanding in the art of drilling, completing and servicing -oil and gas wells is the transmission of information from deep in the wellbore to the surface, such information including pressure, temperature, fluid flow rate, and other parameters desired to be measured at a particular point in the wellbore. During drilling operations it is also desired to be able to determine the actual weight on the drill bit, stresses in the drillstem and bit, bit rotational speed and related parameters.
In regard to transmitting data while drilling, various types of so-called telemetry systems have been developed including mud pulse type systems, electromagnetic systems and acoustic wave transmission systems. Certain shortcomings have been recognized in all of these systems with respect to the quality of the signal received at the surface. However, in pursuing the invention in my U.S. Pat. No. 4,715,451, assigned to the assignee of the present invention, it has been recognized that axial, torsional, and bending vibrations of a drillstem or tubing string at various frequencies and intensities can be sensed at a point at or near the surface with the utilization of high resolution strain gauges and accelerometers suitably mounted on the drillstem or tubing string. Based on experimentation and the development of measuring drillstem and tubing string loading and behavior utilizing the method and apparatus described in the above-mentioned patent, an improved telemetry system has been developed in accordance with the present invention which overcomes the shortcomings of prior art systems and is believed to be suitable for use in drillstems, tubing strings and other elongated tubing members oriented in a borehole and extending to depths of several thousand feet or on the surface along generally horizontal runs or courses, also over distances of at least several thousand feet.